i was using whats app perfectly fine then i changed my plan and i restarted my blackberry 8700 and then whats app wouldnt work and said if you have recently installed it on another device it will need reinstalling so i deleted it and now i cant reinstall it because it says my os is not up to date. i am running 4.5 but says i need 4.6

so my question is: where can i download os 4.6 for blackberry 8700?

thanks for your help